CMYK
A subtractive color model used in print: Cyan, Magenta, Yellow, and Key (black), each 0-100%.
Definition
CMYK stands for Cyan, Magenta, Yellow, Key (black). It's a subtractive color model used in printing — inks absorb light rather than emit it, so combining all four at full produces near-black. The 'K' (key) channel adds true black, since combining CMY inks alone produces a muddy dark brown.
Formula
cmyk(C%, M%, Y%, K%). RGB-to-CMYK conversion: C = 1 - R/255, M = 1 - G/255, Y = 1 - B/255, K = min(C, M, Y), then subtract K from each.
Example
cmyk(0, 100%, 100%, 0) = pure red on press. cmyk(12%, 31%, 0, 0) = Mauve. Most professional print files are submitted in CMYK.